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160 Administering dynamic multipathing (DMP)
Administering DMP using vxdmpadm
Configuring DMP path restoration policies
DMP maintains a kernel thread that re-examines the condition of paths at a
specified interval. The type of analysis that is performed on the paths depends
on the checking policy that is configured.
Note: The DMP path restoration thread does not change the disabled state of the
path through a controller that you have disabled using vxdmpadm disable.
Use the
start restore command to configure one of the following policies:
■ check_all
The path restoration thread analyzes all paths in the system and revives the
paths that are back online, as well as disabling the paths that are
inaccessible. The command to configure this policy is:
# vxdmpadm start restore [interval=seconds] policy=check_all
■ check_alternate
The path restoration thread checks that at least one alternate path is
healthy. It generates a notification if this condition is not met. This policy
avoids inquiry commands on all healthy paths, and is less costly than
check_all in cases where a large number of paths are available. This
policy is the same as check_all if there are only two paths per DMP node.
The command to configure this policy is:
# vxdmpadm start restore [interval=seconds] \
policy=check_alternate
■ check_disabled
This is the default path restoration policy. The path restoration thread
checks the condition of paths that were previously disabled due to hardware
failures, and revives them if they are back online. The command to
configure this policy is:
# vxdmpadm start restore [interval=seconds] \
policy=check_disabled
■ check_periodic
The path restoration thread performs check_all once in a given number
of cycles, and check_disabled in the remainder of the cycles. This policy
may lead to periodic slowing down (due to check_all) if there is a large
number of paths available. The command to configure this policy is:
# vxdmpadm start restore interval=seconds \
policy=check_periodic [period=number]